A system of two inhomogeneous linear functional equations

Additive ρ --functional inequalities

“…See [2,3,4,13] for more information on functional equations. In [8], Gilányi showed that if f satisfies the functional inequality…”

The stability of quadratic α -functional equations

“…A generalization of the Rassias theorem was obtained by Gȃvruta [10] by replacing the unbounded Cauchy difference by a general control function in the spirit of Rassias' approach. See [2,3,7,9,11,12,18] for more information on functional equations.…”